A fabric heater is a planar heater in which an electrode is provided on a fabric. Many techniques for such a fabric heater have ever been proposed.
In a heat generating sheet described in Patent Document 1, one obtained by winding a metal line or a strip foil on a string-shaped insulating line is used as a heating line, and a natural fiber or a synthetic fiber is used as an insulating line. This heat generating sheet is constituted by weaving into such a heating line and insulating line and providing an electrode line to form an electric circuit.
A heating element described in Patent Document 2 is a woven fabric which is formed such that a warp and a woof are woven into. In this heating element, a conductive thread is used as a warp, a non-conductive thread is used as a woof, and heat is generated by applying an electric power.
A net-shaped heater described in Patent Document 3 is one formed by tricot knitting in which a plurality of lines for a heater two-dimensionally sews loops continuously in a longitudinal direction. The diameter of the line for a heater is from 0.02 mm to 0.12 mm, and the periphery of the line is coated with enamel. The pitch of stitches of tricot knitting is from 0.5 mm to 5 mm. A net-shaped heater having such a constitution has an effect that the heater can be in a close contact with a curved surface having a complicated shape.
A planar heater described in Patent Document 4 is a technique which was invented by the present applicant. The planar heater described in Patent Document 4 is provided with a first fabric portion and a second fabric portion. The first fabric portion is provided with two first electrode threads. One of the electrode threads is connected to the positive electrode of a battery; the other first electrode thread is connected to the negative electrode of the battery. One first electrode thread and the other first electrode thread are knitted by using interlock stitch. such that they do not cross with each other. In the second fabric portion, a second electrode thread which is a conductor and a heat generating thread which heats when it is energized are knitted by circular knitting. This planar heater is constituted such that an electric current which is flowed out from a battery flows through the one first electrode thread, second electrode thread, heat generating thread, other second electrode thread, and other first electrode thread in the order mentioned, and the heat generating thread is heated.